Mixing, aeration or oxygenating apparatus

ABSTRACT

A mixing, aerating or oxygenating apparatus to aerate or oxygenate ponds, rivers or lakes, sewage or effluent treatment lagoons or beds or to airstrip volatile compounds from water or other solutes by distributing gas through a piped system having a plurality of outlets branching from a common distribution line. In order to deliver a desired quantity of air or oxygen at each outlet, a constant flow regulator is disposed in each outlet which limits the flow to a set amount when the pressure in the pipe system exceeds a predetermined minimum value. In one embodiment, the regulator is chosen to achieve this irrespective of pressure drop along the distribution line. In another embodiment, the regulator is chosen to give the desired output with no pressure drop along the distribution line.

The present invention relates to a method and apparatus for regulatingthe distribution of gaseous fluids and in particular to a mixing,aerating or oxygenating method and apparatus to aerate or oxygenateponds, rivers, estuaries, reservoirs or lakes, sewage or effluenttreatment lagoons beds or tanks or to airstrip volatile compounds fromwater or other solutes.

There are many situations where submerged diffusers are used tointroduce gas into a liquid. For example to transfer oxygen into aliquid (typically water) for the purposes of aeration and mixing, andespecially to oxygenate the water. Such techniques are used in aerobicbiological treatments systems as used to treat sewage, effluents ofvarious types, and storm water and water in aquaria or lakes and rivers,among others. They are also used for air stripping of volatile organicsfrom contaminated water.

It is common to treat sewage in “activated sludge treatment plants” byfeeding precise volumes of air to a plurality of diffusers which releasethe air into the water in precise small bubbles to stimulate naturalprocesses. The number of diffusers and hence the spacing is calculatedrelative to the volume of water to be treated and the amount oftreatment required. The diffusers are usually placed at the lowest pointin the water column allowing the most time for air to pass through thewater prior to reaching the atmosphere.

In the known systems a plurality of diffusers are fed from a supplyline, usually from a suitable air source such as an air pump, whichdelivers a constant and even supply of air. The diffusers are disposedin series along the supply line and the quantity of air emerging fromeach diffuser is intended to be substantially the same. In the knownsewage treatment systems potential pressure drop along the line from onediffuser to the next is rendered negligible by utilising a supply pipehaving a large cross-sectional area and a relatively low-pressuresupply. The cross-section of the pipe has to be calculated having regardto the number of diffusers and the discharge rate in order to ensurethat there is a negligible pressure drop along the length of the pipeand thereby ensure that the flow from the diffusers is balanced. Inother specific aeration systems a manually adjustable valve or orifacecontrol may be provided for each diffuser to balance their output. Theknown system of individually balanced gas diffusers is difficult to setup to ensure correct balance, usually requiring accurate levelling ofthe outlet diffusers.

A constant flow regulator and a method of manufacturing same comprisinga moving “0” ring is described in patent Nos. EP 115342 and GB 2136713.The described regulator gives a constant through volume flow rate ofliquid over a wide range of supply pressures. A regulator of this typecan be designed to produce a specific flow rate over a prescribedpressure range and can be moulded from plastics which makes themextremely economical to produce. When a plurality of such constant flowdevices are fitted in series in a pipeline supplied with liquid at asufficiently high pressure, the flow rate is constant from eachregulated line irrespective of the pressure fluctuations along thepipeline(s) of the system. The supply line pressure has to be above apre-determined minimum level at the point where the pressure drop ishighest. Usually this will be at the end of the pipeline. The use ofthese devices has not been considered to regulate the flow of air oroxygen. There is no teaching to use these devices with fluids other thanliquids. The reason for this may be that none of the commerciallyavailable devices have been deemed able to operate to produce constantflow with fluctuating air pressure.

It is an aim of the present invention to provide a gas distributionsystem which overcomes the current difficulties.

One aspect of the invention provides a method of distributing gasthrough a piped system having a plurality of outlet lines branching froma common supply line or manifold, the method comprising continuouslygenerating a predetermined minimum volume of gas and introducing it intothe pipe system, delivering a desired quantity of gas at each of theoutlets by providing a constant flow regulator means in each outlet linewhich limits the flow to a set amount when the pressure in the pipesystem exceeds a predetermined minimum value.

More particularly, the present invention provides a method of mixing,aerating or oxygenating ponds, rivers or lakes, sewage/treatment lagoonsor effluent beds or air striping volatile compounds from water or othersolutes, the method comprising distributing air or oxygen through apiped system having a plurality of outlet lines branching from a commonsupply line or manifold, by continuously generating a predeterminedminimum volume of air or oxygen and introducing it into the pipe system,delivering a desired quantity of the air or oxygen at each of theoutlets by providing a constant flow regulator means in each outlet linewhich limits the flow to a set amount when the pressure in the pipesystem exceeds a predetermined minimum value.

For the aforementioned applications the gas as referred to hereinafterwill be air or oxygen.

More particularly the predetermined minimum volume of gas exceeds acalculated minimum volume which is required to be delivered by thediffusers. Preferably a moving element control flow regulator is chosento achieve this irrespective of pressure drop along the pipe, at leastwithin a pressure range which is deemed acceptable. For mostapplications an accurate and even quantity of gas is delivered at eachoutlet. This can be achieved using constant flow regulators having aspecific and even flow rating for each outlet.

Another aspect of the present invention provides a gas distributionsystem comprising a gas distribution supply line, a source of gaspressure connected to the distribution supply line, and a plurality ofoutlet lines branching from the distribution supply line, andcharacterised by a constant flow regulator disposed between thedistribution supply line and each outlet line to cause a desired flow ofgas to be delivered through the outlet lines.

More particularly, the present invention provides a mixing, aeration oroxygenation system to aerate or oxygenate ponds, rivers, estuaries,reservoirs or lakes, sewage or effluent treatment lagoons or beds or toairstrip volatile compounds from water or other solutes and comprisingan air or oxygen distribution supply line, a source of air or oxygenpressure connected to the distribution supply line, and a plurality ofoutlet lines branching from the distribution supply line, andcharacterised by a constant flow regulator disposed in each outlet lineto cause a desired flow of air or oxygen to be delivered through theoutlet lines.

For the aforementioned application the gas referred to herewith will beair or oxygen. There may be more than one distribution line.

More particularly a predetermined minimum volume of gas is supplied,which volume is calculated to exceed the minimum volume which is to bedelivered from the diffusers. The desired flow of gas is a desired evenflow of gas.

The constant flow regulator may be a moving “0” ring constant flowregulator or other moving element constant flow regulator which isprecisely tuned to deliver the desired calculated supply of gas requiredat the outlet line irrespective of changes in supply pressure such thatit is self compensating for changes in supply pressure within itsdesigned operating range.

In an alternative, a moving “O” ring regulator is used that only allowsa desired maximum flow (volume) of gas to pass through above a knownpressure of gas. Using such a regulator, pressure drops along thepipeline can be compensated for by using a regulator which has thedesired maximum flow at a lower pressure to reflect the pressure drop.By this means a substantially even flow of gas is achieved from all theoutlets. It will be understood that when the term even is used, therewill most usually be an acceptable tolerance variation to the desiredflow rate.

Each outlet line has a suitable outlet nozzle. They may be aerationnozzles, diffusers or any other suitable nozzle for the intendedapplication. In a preferred application each outlet line supplies arespective diffuser. Conveniently the outlet lines are disposed inseries along the distribution supply line. The number of outlet linesand hence outlet nozzles/diffisers are calculated and spaced accordingto the particular application. Preferably the gas originates from asuitable source, usually generated by a pump gas blower or generator orother suitable device, and preferably it delivers a constant volume ofgas. The system can be used for distributing any desired gascomposition. For many applications the gas will be air other gases couldbe oxygen, carbon dioxide, nitrogen or ozone. The distribution supplyline comprises at least one length of pipe. As an alternative it maycomprise a plurality of lengths of pipe branching from a common manifoldor having a direct connection with the supply of gas. The pipeline mayinclude a return line or be of ring main type. The outlet lines mayincorporate a backflow regulation device and/or an isolation ball valve.Such devices may incorporate the aforesaid constant flow regulator or beprovided as separate devices. The constant flow regulator, any backflowregulation device and any isolation valve may be combined with an outletdiffuser.

The invention can be used for a large number of potential applications,for example the treatment sewage, leachate and agricultural waste waterby the introduction of air, air stripping of volatile compounds fromwater or other solutes, mixing water columns, aerating and mixing ofaquaria, ponds, lakes and rivers or tanks containing fish, and inconnection with various industrial processes. Where the system is usedfor the purpose of introducing gas into a liquid or other gas, thebackflow prevention device avoids the liquid or gas entering the systemshould the system enter a state of relative negative pressure. Theisolation ball valve allows individual branches to be isolated. Thesystem can be used to control a bubble curtain.

For any given application the delivery rate from the outlet lines willbe known and the source of gas will be capable of maintaining a constantsupply of no less than the calculated minimum requirement for thesystem.

The present invention may be used for any of the above mentionedapplications and any other applications in which gas, and in particularair or oxygen is to be transferred to a liquid.

The present invention will now be described further hereinafter, by wayof example only, with reference to the accompanying drawings; in which:—

FIG. 1 shows schematically one embodiment of air distribution systemembodying the present invention, and

FIG. 2 is a graph of flow rate against pressure for a preferred pressureregulator.

For convenience the present invention is described by way of example inrelation to the treatment of water by the injection of air. In oneapplication for waste treatment the water will contain effluent. Thewater/effluent to be treated is shown at 1 and held within an open wellor receiver 3. An air distribution pipeline 2 extends from a source ofair 1 which supplies the air under pressure to the pipeline. A motordriven pump (not illustrated) conveniently serves this purpose. Thepipeline 2 has a plurality of outlets 4 disposed along the lengththereof at spaced intervals. For the purpose of effluent treatment eachoutlet is provided with a diffuser which releases the air into thewater/effluent in the form of small bubbles. In order to ensure that theflow of air from each diffuser is the same, a regulator 5 isincorporated into the flow line between the pipework 2 and the outletdiffuser 4. The regulator may be part of the diffuser or a separatecomponent. The regulator is designed to deliver a constant flowirrespective of pressure variations in the pipeline when the pressure inthe pipeline exceeds a predetermined minimum value, which minimum valueis calculated to be that which will ensure that each regulator suppliesthe desired volume of gas. The preferred regulator device is of a typeknown as a moving element constant flow regulator such as described inthe above mentioned patents. These are very economical to produce,especially when moulded from plastics.

The preferred moving element regulator is designed to operate to delivera desired flow of air over a range of supply pressures. That is to sayit is self-compensating for changes in supply pressure over a prescribedrange of pressures above a minimum pressure level. FIG. 2 is a graph ofa constant pressure regulator of moving element type havingcharacteristics of the described type and shows flow volume againstpressure. It shows how the flow rate plateaus after pressure P1. Using aplurality of flow regulators in a distribution supply line will giverise to an even delivery of air from the plurality of diffusersproviding the pressure in the pipeline exceeds the minimum thresholdvalue P1.

In an alternative, using an “O” ring type regulator, the regulator onlyallows a set maximum flow (volume) of air to pass through at a givenpressure of air providing the pressure in the system does not exceedthat given pressure, then the flow rate from each outlet line will be atthe set maximum flow, rate, and a regulator is chosen which provides thedesired flow rate for a particular application. This can be used wherethere is little or no pressure drop along the distribution line.

1. A method of mixing, aerating or oxygenating ponds, rivers or lakes,sewage/treatment lagoons or effluent beds or air striping volatilecompounds from water or other solutes, the method comprisingdistributing air or oxygen through a piped system having a plurality ofoutlet lines (4) branching from a common supply line or manifold (2),characterised by continuously generating a predetermined minimum volumeof air or oxygen and introducing it into the pipe system, delivering adesired quantity of the air or oxygen at each of the outlets byproviding a constant flow regulator means (5) in each outlet line whichlimits the flow to a set amount when the pressure in the pipe systemexceeds a predetermined minimum value.
 2. A method as claimed in claim 1in which the minimum volume of air or oxygen exceeds a calculatedminimum volume which is required to be delivered from the outlets.
 3. Amethod as claimed in claims 1 or 2 in which substantially the samequantity of air or oxygen is delivered at each outlet irrespective ofpressure drop along the pipe, at least within a flow range which isdeemed acceptable.
 4. A method as claimed in anyone of claims 1 to 3 inwhich a moving element constant flow regulator is used.
 5. A method asclaimed in claim 1 in which the pressure is kept substantially constantalong the distribution line and an accurate and even quantity of air oroxygen is delivered at each outlet using a moving “O” ring constant flowregulator which operates at its set maximum flow rate at the setpressure.
 6. A mixing, aeration or oxygenation system to aerate oroxygenate ponds, rivers, or lakes, sewage or effluent treatment lagoonsor beds or to airstrip volatile compounds from water or other solutesand comprising an air or oxygen distribution supply line (2), a sourceof air or oxygen pressure connected to the distribution supply line, anda plurality of outlet lines (4) branching from the distribution supplyline, and characterised by a constant flow regulator (5) disposed ineach outlet line to cause a desired flow of air or oxygen to bedelivered through the outlet lines.
 7. A system as claimed in claim 6 inwhich a predetermined minimum volume of air or oxygen is supplied, whichvolume is calculated to exceed the minimum volume which is to bedelivered from all the outlets from the outlet lines.
 8. A system asclaimed in claims 6 or 7 in which the desired flow of air or oxygen is adesired even flow of air or oxygen.
 9. A system as claimed in anyone ofclaims 6 to 8 in which the regulator is tuned to deliver the desiredcalculated supply of air or oxygen required at the outlet lineirrespective of changes in supply pressure such that it is selfcompensating for changes in supply pressure within its designedoperating range.
 10. A system as claimed in anyone of claims 6 to 8 inwhich the regulator is designed to only allow a desired maximum flow(volume) of air or oxygen to pass through at a known pressure of air oroxygen.
 11. A system as claimed in claim 10 in which the constant flowregulator comprises an “O” ring moving element ring constant flowregulator.
 12. A system as claimed in anyone of claims 6 to 11 in whicheach outlet line has a suitable outlet nozzle.
 13. A system as claimedin claims 6 to 12 in which the outlet lines are disposed in series alongthe distribution line.
 14. A system as claimed in anyone of claims 6 to13 in which the source of air or oxygen pressure is a pump whichdelivers a constant volume of air or oxygen.
 15. A system as claimed inanyone of claims 6 to 14 in which the distribution supply line comprisesat least one length of pipe.
 16. A system as claimed in anyone of claims6 to 15 in which the distribution supply line comprises a plurality oflengths of pipe branching from a common manifold or having a directconnection with the supply of air or oxygen.
 17. A system as claimed inanyone of claims 6 to 16 in which the pipeline includes a return line oris of ring main type.
 18. A system as claimed in anyone of claims 6 to17 in which the outlet lines incorporate a backflow regulation deviceand/or an isolation ball valve.
 19. A method of mixing, aerating oroxygenating ponds, rivers or lakes, sewage/treatment lagoons or effluentbeds or air striping volatile compounds from water or other solutes, bydistributing air or oxygen through a piped system when constructed andarranged substantially as hereinbefore described with reference to theaccompanying drawings.
 20. A mixing, aeration or oxygenation system toaerate or oxygenate ponds, rivers, or lakes, sewage or effluenttreatment lagoons or beds or to airstrip volatile compounds from wateror other solutes constructed and arranged substantially as hereinbeforedescribed with reference to and as illustrated in the accompanyingdrawings.